Suggest me some software for keeping track of my hours worked

Hi all, 

I'm an entrepreneur and as such need to keep track of the amount of hours I work, as I need to reach a certain minimum. 

My needs are quite minimal. I want the following fields: 

• A date drop down; 
• a category selection drop down (PR, financial, etc); 
• a field for comments; 
• and I want to enter an amount of hours worked (I would prefer not to have to enter a start time and end time separately as that is more actions to perform and more than I need) 

Ideally this would be editable on my phone as well as on my PC, and being able to quickly add up the hours worked would of course also be helpful. And being able to see a calendar overview, perhaps. 

I have a self-hosted server, so I could simply make a spreadsheet and edit that, but that still seems like it's not as fast and easy as I'd like. 

I've been trying out Pendulums, but their system of clocking in and out doesn't fit my type of activities, and manually entering them gives me too much to have to click on (including start time and end time, while I just want to enter an amount of hours). 

I much prefer open source software, but I've been having a hard time finding something to fit my use case. I imagine that for my case, it doesn't need to be something that's specifically for keeping track of hours worked—something that provides some kind of frontend to fill in a spreadsheet would suffice, I imagine. 

Does anyone have any ideas for FOSS that could do something like this?